WO2022050094A1

WO2022050094A1 - Filter module, filter element and electronic device

Info

Publication number: WO2022050094A1
Application number: PCT/JP2021/030662
Authority: WO
Inventors: 賢太郎三川; 健一石塚
Original assignee: 株式会社村田製作所
Priority date: 2020-09-02
Filing date: 2021-08-20
Publication date: 2022-03-10
Also published as: JPWO2022050094A1; CN116057649A; US20230199942A1

Abstract

This filter module 101 is provided with a circuit substrate 20 having a ground electrode formed thereon, and a low pass filter 11 mounted on the circuit substrate 20. The low-pass filter 11 is provided with a first inductor L1, a second inductor L2 and a capacitor C2, the first inductor L1 and the second inductor L2 are connected additively, and the relations Lp + Lg - M ≥ 0 and Lp - M < 0 hold when Lp represents the inductance of the path between the ground terminal GND and the connection CP between the first inductor L1 and the second inductor L2, Lg represents the inductance of the path between the ground terminal GND and the ground electrode, and M represents the mutual inductance between the first inductor L1 and the second inductor L2.

Description

Filter modules, filter elements and electronic devices

The present invention relates to a filter module in which a high-frequency filter circuit is configured, a filter element used in this filter module, and an electronic device including the same.

Patent Document 1 discloses a low-pass filter composed of two coils formed inside a laminated body and a plurality of capacitors. These two coils are spiral coils each having a central axis extending in the stacking direction of the plurality of insulator layers.

Japanese Unexamined Patent Publication No. 2013-21449

The low-pass filter described in Patent Document 1 has a structural parasitic inductor between the connection portion of the two coils inside and the ground terminal.

Further, the low-pass filter described in Patent Document 1 is used by being mounted on a circuit board. The ground terminal of this low-pass filter is connected to the ground terminal of the circuit board, but there is also a parasitic inductor between the ground terminal of the circuit board and the reference potential electrode of the circuit board (usually the ground electrode that spreads over a wide area). ..

The above will be described with reference to FIGS. 12A and 12B. FIG. 12A is an equivalent circuit diagram of the low-pass filter shown in Patent Document 1, and FIG. 12B is an equivalent circuit diagram in a state where the low-pass filter is mounted on a circuit board.

In FIG. 12A, the low-pass filter 10 includes a first terminal T1, a second terminal T2, and a ground terminal GND, and the low-pass filter is configured by the series-connected inductors L1 and L2 and the shunt-connected capacitors C1, C2, and C3 to the ground. Will be done.

However, an inductance component such as a parasitic inductance is generated between the connection portion CP between the inductor L1 and the inductor L2 and the ground terminal GND. The inductor Lp in FIG. 12A is an element that clearly shows this inductance component. Since this inductance component Lp resonates with the capacitor C2 connected in series with it, an attenuation pole is generated at the resonance frequency, and the amount of attenuation decreases in a frequency band higher than that, so that attenuation occurs in a wide band on the high frequency band side. Difficult to use when needed.

Further, as shown in FIG. 12B, the circuit board 20 on which the low-pass filter 10 is mounted has a reference potential electrode (a ground electrode that spreads over a wide area) of the circuit board and a ground terminal to which the ground terminal GND of the low-pass filter 10 is connected. An inductance component such as a parasitic inductance is generated between the connection pad and the connection pad. The inductor Lg in FIG. 12B is an element that clearly shows this inductance component. Therefore, in the actual use state, the combined inductance of the inductance component Lp and the inductance component Lg resonates with the capacitance of the capacitor C2, and an attenuation pole is generated at the resonance frequency. Therefore, the amount of attenuation decreases in the frequency band higher than this attenuation pole.

On the other hand, in recent applications, there is a tendency for the frequency band to secure a predetermined amount of attenuation in the attenuation range to expand. For example, in a low-pass filter that cuts off a high-frequency wideband frequency band such as 5G (5th Generation) or UWB (Ultra Wide Band), the frequency band to be attenuated extends over a wide band. Therefore, it is required that the amount of attenuation in the attenuation region of the low-pass filter is secured over a wide band.

Therefore, an object of the present invention is to provide a filter module having good attenuation characteristics over a wide band on the high frequency side of the passing region, a filter element used for this filter module, and an electronic device including them.

(1) The filter module as an example of the present disclosure is a filter module composed of a circuit board on which a ground electrode is formed and a filter element mounted on the circuit board, and the filter element is the first. The first inductor and the second inductor, which are connected in series between the terminal and the second terminal and are magnetically coupled to each other, are connected between the connection portion between the first inductor and the second inductor and the ground terminal. The first inductor and the second inductor are connected in sum to each other, and the magnetic field coupling between the first inductor and the second inductor causes between the connection portion and the ground terminal. When the mutual inductance is represented by M, the inductance between the connection portion and the ground terminal is represented by Lp, and the inductance of the path between the ground terminal and the ground electrode is represented by Lg, Lp + Lg−M ≧ 0 and Lp− It is characterized in that it has a relationship of M <0.

With the above configuration, the connection between the first inductor and the second inductor and the ground electrode of the circuit board due to the negative mutual inductance generated in the path shunted to the ground terminal due to the magnetic field coupling between the first inductor and the second inductor. The combined inductance component generated between and is suppressed, and the resonance frequency due to this combined inductance and the capacitance of the capacitor moves to a higher range than the frequency band used. Further, since the relationship of Lp + Lg−M ≧ 0, an attenuation pole is generated due to resonance between the combined inductance and the capacitance of the capacitor.

(2) The filter element as an example of the present disclosure is a filter element mounted on a circuit board on which a ground electrode is formed, and is a ground terminal connected to the ground electrode, and a first terminal and a second terminal. A first inductor and a second inductor that are connected in series to each other and are magnetically coupled to each other, and a capacitor that is connected between the connection portion between the first inductor and the second inductor and the ground terminal. The first inductor and the second inductor are connected in a summoned manner, and the mutual inductance generated between the connection portion and the ground terminal due to the magnetic field coupling between the first inductor and the second inductor is represented by M. When the inductance between the connection portion and the ground terminal is expressed by Lp, it is characterized in that there is a relationship of Lp-M <0.

With the above configuration, the connection between the first inductor and the second inductor and the ground electrode of the circuit board due to the negative mutual inductance generated in the path shunted to the ground terminal due to the magnetic field coupling between the first inductor and the second inductor. The combined inductance component generated between and is suppressed, and the resonance frequency due to this combined inductance and the capacitance of the capacitor moves to a higher range than the frequency band used.

(3) An electronic device as an example of the present disclosure includes the filter module or the filter element.

According to the present invention, a filter module having good attenuation characteristics over a wide band, a filter element used for this filter module, and an electronic device including the same can be obtained on the high frequency side of the passing region.

FIG. 1A is a circuit diagram of the filter module 101 according to the first embodiment. FIG. 1B is an equivalent circuit diagram of the filter module 101. FIG. 2 is an equivalent circuit diagram showing the mutual inductance generated by the magnetic field coupling between the first inductor L1 and the second inductor L2 as a circuit element. 3A and 3B are perspective views of the low-pass filter 11. FIG. 4 is an exploded bottom view showing each insulator layer of the low-pass filter 11 and the conductor pattern formed on them. FIG. 5 is a diagram showing the frequency characteristics of the transmission coefficient of the filter module 101. FIG. 6 is a perspective view of the filter module 102 according to the second embodiment. FIG. 7 is a front view of the filter module 102. FIG. 8 is a diagram showing the frequency characteristics of the transmission coefficient of the filter module 102. FIG. 9A is a circuit diagram of the filter module 103 according to the third embodiment. FIG. 9B is an equivalent circuit diagram of the filter module 103. FIG. 10 is a diagram showing the frequency characteristics of the transmission coefficient of the bandpass filter 13. FIG. 11 is a block diagram showing the configuration of the electronic device 201 according to the fourth embodiment. FIG. 12A is an equivalent circuit diagram of the low-pass filter shown in Patent Document 1, and FIG. 12B is an equivalent circuit diagram in a state where the low-pass filter is mounted on a circuit board.

Hereinafter, a plurality of embodiments for carrying out the present invention will be shown with reference to the drawings with reference to some specific examples. The same reference numerals are given to the same parts in each figure. Although the embodiments are shown separately in a plurality of embodiments for convenience of explanation in consideration of the explanation of the main points or the ease of understanding, partial replacement or combination of the configurations shown in different embodiments is possible. In the second and subsequent embodiments, the description of matters common to the first embodiment will be omitted, and only the differences will be described. In particular, the same action and effect due to the same configuration will not be mentioned sequentially for each embodiment.

<< First Embodiment >>
FIG. 1A is a circuit diagram of the filter module 101 according to the first embodiment. FIG. 1B is an equivalent circuit diagram of the filter module 101. The filter module 101 includes a low-pass filter 11 and a circuit board 20 on which a ground electrode is formed.

The low-pass filter 11 shown in FIG. 1A includes a first terminal T1, a second terminal T2, and a ground terminal GND. Further, the low-pass filter 11 is connected in series between the first terminal T1 and the second terminal T2, and is magnetically coupled to each other, the first inductor L1 and the second inductor L2, and the first inductor L1 and the second inductor L2. A capacitor C2 connected between the connection portion CP with and the ground terminal GND is provided. Hereinafter, the code of the inductor and the code of the inductance of the inductor are used in common. Therefore, for example, the inductance of the inductor L1 is indicated by L1.

An inductance component Lp such as a parasitic inductance is generated between the connection portion CP between the first inductor L1 and the second inductor L2 and the ground terminal GND shown in FIG. 1A. In FIG. 1B, this inductance component is represented by an inductor Lp.

The ground electrode of the circuit board 20 is a reference potential electrode of the circuit board 20, and is usually an electrode that spreads over a wide area. That is, in the present specification, the "ground electrode" is a planar electrode that serves as a reference potential in the circuit. As shown in FIG. 1B, an inductance component Lg such as a parasitic inductance is generated between the reference potential electrode of the circuit board 20 and the ground terminal connection pad to which the ground terminal GND of the low-pass filter 10 is connected. In FIG. 1B, this inductance component is represented by the inductor Lg.

FIG. 2 is an equivalent circuit diagram showing the mutual inductance generated by the magnetic field coupling between the first inductor L1 and the second inductor L2 as a circuit element. As shown in FIG. 2, when the circuit connected between the first terminal T1 and the second terminal T2 is represented by a T-type equivalent circuit using inductors LA, LB, and LC, the inductor LC representing the mutual inductance is a series. A shunt connection is made between the connection points of the connected inductors LA and LB and the ground terminal GND. Since the first inductor L1 and the second inductor L2 are connected in harmony, the inductance of the inductor LA is (L1 + M), the inductance of the inductor LB is (L2 + M), and the inductance of the inductor LC is (−M).

With the above configuration, a negative mutual inductance (-M) is generated in the path shunt-connected to the ground terminal GND due to the magnetic field coupling between the first inductor L1 and the second inductor L2. Due to this negative mutual inductance (−M), the inductance component generated between the connection portion CP between the first inductor L1 and the second inductor L2 and the ground electrode of the circuit board 20 is suppressed. Therefore, the resonance frequency (attenuated pole frequency) due to the combined inductance of the negative mutual inductance (−M), the inductance component Lp and the inductance component Lg, and the capacitance of the capacitor C2 moves higher than the frequency band used.

Incidentally, in the low-pass filter described in Patent Document 1, since the two coils are differentially connected, the mutual inductance generated by the magnetic field coupling is positive, so that the two coils are connected to the shunt to the ground terminal GND of the low-pass filter. The combined inductance generated in the path is even larger.

In FIG. 1B, the relationship between the inductance component Lg generated between the ground electrode of the circuit board 20 and the ground terminal GND of the low-pass filter 11, the inductance component Lp, and the mutual inductance (-M) is as follows.

Lp + Lg-M ≧ 0
Lp-M <0
As a result, the inductance component Lg is suppressed by the negative inductance (Lp-M). Further, when Lp + Lg−M ≧ 0, an attenuation pole is generated due to resonance between the combined inductance and the capacitance of the capacitor C2.

3A and 3B are perspective views of the low-pass filter 11. The viewpoints are different between FIGS. 3A and 3B. In addition, all of them transparently represent the inside.

The low-pass filter 11 includes a rectangular parallelepiped laminated body 1 in which a plurality of rectangular insulator layers are laminated. A first terminal electrode ET1, a second terminal electrode ET2, and two ground terminal electrodes EGND are formed on the outer surface of the laminated body 1.

The first inductor L1 is composed of a coiled conductor CL1 formed on a laminated body 1 of a plurality of insulator layers, and the second inductor L2 is a coiled conductor formed on a laminated body 1 of a plurality of insulator layers. It is composed of the conductor CL2.

Capacitor C2 is composed of capacitor electrodes C2a, C2b, C2c facing each other in the stacking direction of a plurality of insulator layers and an insulator layer sandwiched between these capacitor electrodes.

The connection portion between the coiled conductor CL1 of the first inductor L1 and the coiled conductor CL2 of the second inductor L2 and the capacitor electrode C2b are connected via the interlayer connection conductor V.

One end of the coiled conductor CL1 of the first inductor L1 is conducting to the first terminal electrode ET1, and one end of the coiled conductor CL2 of the second inductor L2 is conducting to the second terminal electrode ET2. The capacitor electrodes C2a and C2c are conductive to the ground terminal electrode EGND, and the capacitor electrodes C2b are connected to the coiled conductor CL1 of the first inductor L1 and the coiled conductor CL2 of the second inductor L2 via the interlayer connection conductor V. It is conducting to the connection part.

FIG. 4 is an exploded bottom view showing each insulator layer of the low-pass filter 11 and the conductor pattern formed on them.

The laminated body 1 is formed by laminating the insulator layers S1 to S11. FIG. 4 shows a bottom view of each insulator layer. The insulator layer S1 is the uppermost insulator layer, and the insulator layer S11 is the lowest insulator layer. The insulator layers S2 to S10 are insulator layers between the uppermost insulator layer S1 and the lowermost insulator layer S11.

The coiled conductors CL1a, CL1b, CL1c, and CL1d formed in the insulator layers S1 to S4 constitute the coiled conductors CL1 shown in FIGS. 3A and 3B. Similarly, the coiled conductor CL2 is configured by the coiled conductors CL2a, CL2b, CL2c, and CL2d.

Further, the capacitor C2 is composed of the capacitor electrodes C2a, C2b, C2c formed in the insulator layers S8 to S10 and the insulator layers S9, S10.

When the coiled conductors CL1 and CL2 are viewed in the WA direction of the winding axis (see FIGS. 3A and 3B), the coiled conductors CL1 and CL2 have at least a part not overlapping with the capacitor electrodes C2a, C2b and C2c. As a result, unnecessary parasitic capacitance generated between the coiled conductors CL1 and CL2 and the capacitor electrodes C2a, C2b and C2c is suppressed.

Side terminal electrodes E1 and E2 are formed on the insulator layers S1 to S11. Further, side terminal electrodes E1, E2, E3, and E4 are formed on the insulator layers S8 to S10. The side terminal electrodes E1, E2, E3, and E4 formed in each insulator layer are electrically connected to each other with the same reference numerals.

One end of the coiled conductor CL1a conducts to the side terminal electrode E1, and one end of the coiled conductor CL2a conducts to the side terminal electrode E2. The capacitor electrode C2a and the capacitor electrode C2c are electrically connected to the side terminal electrodes E3 and E4, respectively.

Looking in the direction of the winding axis WA of the coiled conductor, the capacitor electrodes C2a, C2b, and C2c have a portion that does not overlap with the first terminal electrode ET1 and the second terminal electrode ET2. As a result, unnecessary parasitic capacitance generated between the capacitor electrodes C2a, C2b, C2c and the first terminal electrode ET1 and the second terminal electrode ET2 is suppressed. It should be noted that the capacitor electrodes C2a, C2b, and C2c may have a structure in which the capacitor electrodes C2a, C2b, and C2c do not overlap with one of the first terminal electrode ET1 and the second terminal electrode ET2 when the winding axis WA direction of the coiled conductor is viewed. For example, if the capacitors C2a, C2b, and C2c have a structure having a portion that does not overlap with the first terminal electrode ET1, the parasitic capacitance between the capacitors C2 and the first terminal T1 shown in FIG. 1A can be suppressed. Similarly, if the capacitors C2a, C2b, and C2c have a structure having a portion that does not overlap with the second terminal electrode ET2, the parasitic capacitance between the capacitor C2 and the second terminal T2 can be suppressed.

Each of the insulator layers S1 to S11 of the laminate 1 is formed by screen printing, exposure and development of the photosensitive insulating paste and the photosensitive conductive paste, and the laminate 1 is formed by laminating the insulator layers S1 to S11. To.

Specifically, the photosensitive insulating paste layer is screen-printed, irradiated with ultraviolet rays, and developed with an alkaline solution. This forms an insulating substrate pattern with openings for external electrodes, via holes, and the like. Further, the photosensitive conductive paste is screen-printed, irradiated with ultraviolet rays, and developed with an alkaline solution to form a conductor pattern. A mother laminated body is obtained by laminating the insulating base material pattern and the conductor pattern. Then, a large number of laminated bodies 1 are obtained by dividing the mother laminated body into individual pieces. The surface of each external electrode is, for example, Ni / Au plated for the purpose of improving solderability, conductivity, and environmental resistance.

The method for forming the laminated body 1 is not limited to this. For example, a method of printing and laminating a conductor paste using a screen plate opened in a conductor pattern shape may be used. Further, the conductor foil may be attached to the insulating base material, and the conductor pattern of each insulator layer may be formed by patterning the conductor foil. The method for forming the external electrode is not limited to this, and for example, an external electrode may be formed on the bottom surface and the side surface of the laminated body 1 by dipping a conductor paste on the laminated prime field or a sputtering method, and further, the external electrode may be formed on the surface thereof. It may be plated.

FIG. 5 is a diagram showing the frequency characteristics of the transmission coefficient of the filter module 101. The horizontal axis of FIG. 5 is the frequency, and the vertical axis is the transmission coefficient. In FIG. 5, the characteristic A is the characteristic of the low-pass filter 11 of the present embodiment, and the characteristics B, C, and D are the characteristics of the filter module as a comparative example. The characteristic B is a characteristic when the mutual inductance M shown in FIGS. 1A and 1B is set to 0.

Comparing the characteristic A of the filter module 101 of the present embodiment with the characteristic B of the filter module of the comparative example, the passing frequency band is the 2.4 GHz band used as a wireless LAN, and the insertion loss is -3 dB. The cutoff frequency is about 4.5 GHz, but the attenuation pole frequency of the characteristic B of the filter module of the comparative example is 8.5 GHz, whereas the attenuation pole frequency of the filter module 101 of the present embodiment is 12.5 GHz. be.

As indicated by the arrow symbols in FIG. 5, when the frequency difference between the cutoff frequency and the attenuation pole frequency is small, the amount of attenuation jumps sharply from the decay pole frequency to the high frequency range, and the jump is large (attenuation is large). Shallower). When the frequency difference between the cutoff frequency and the attenuation pole frequency is large, the amount of attenuation jumps slowly from the decay pole frequency to the high frequency range, and the jump is small (deeper attenuation). Therefore, the filter module 101 of the present embodiment has a larger amount of attenuation in the high frequency region than the attenuation pole, as compared with the filter module as a comparative example showing the characteristic B. This is because the inductance component Lp generated between the connection portion CP between the first inductor L1 and the second inductor L2 and the ground terminal GND and the inductance component Lg of the circuit board are suppressed by the negative mutual inductance (-M). Is.

In FIG. 5, the characteristic C is the combined inductance (Lp + Lg−) of the inductance component Lp, the inductance component Lg, and the mutual inductance (−M) generated between the connection portion CP between the first inductor L1 and the second inductor L2 and the ground electrode. This is a characteristic when M) is 0. The characteristic D is a characteristic when the combined inductance (Lp + Lg-M) is negative. As described above, when the combined inductance of the inductance component Lp, the inductance component Lg, and the mutual inductance (−M) is 0 or negative, resonance does not occur with the capacitor C2, so that no attenuation electrode is generated. Therefore, it is not possible to secure a predetermined amount of attenuation in a frequency range higher than the cutoff frequency. Further, when the combined inductance of the inductance component Lp, the inductance component Lg, and the mutual inductance (−M) is negative, the steepness is significantly deteriorated, and it becomes more difficult to obtain deep attenuation over a wide band. Therefore, it is desirable that the combined inductance (Lp + Lg-M) is positive.

<< Second Embodiment >>
In the second embodiment, a filter module composed of a low-pass filter and a circuit board on which the low-pass filter is mounted will be illustrated.

FIG. 6 is a perspective view of the filter module 102 according to the second embodiment. FIG. 7 is a front view of the filter module 102. A pad for connecting each terminal of the low-pass filter 11 is formed on the upper surface of the circuit board 20. Further, a continuous wiring electrode 31 is formed from a pad to which the ground terminal electrode EGND of the low-pass filter 11 is connected. A ground electrode 30 is formed on the lower surface of the circuit board 20. The ground electrode 30 is a reference potential electrode of the circuit board 20, and extends over a wide area. In the present embodiment, the area of the ground electrode 30 is larger than the square of the long side of the rectangle when the low-pass filter 11 is viewed in a plane. Inside the circuit board 20,

interlayer connection conductors

32A and 32B are formed to connect the wiring electrode 31 on the upper surface and the ground electrode 30 on the lower surface. Therefore, the ground terminal electrode EGND of the low-pass filter 11 conducts to the ground electrode 30 of the circuit board 20 through the path of [wiring electrode 31]-[

interlayer connection conductors

32A, 32B]-[ground electrode 30].

The inductance component of the wiring electrode 31 and the inductance components of the

interlayer connection conductors

32A and 32B correspond to the inductance component Lg shown in FIG.

FIG. 8 is a diagram showing the frequency characteristics of the transmission coefficient of the filter module 102. The horizontal axis of FIG. 8 is the frequency, and the vertical axis is the transmission coefficient. In this example, the passing frequency band is the 2.4 GHz band used as a wireless LAN, the cutoff frequency at which the insertion loss is -3 dB is about 4 GHz, and the attenuation pole frequency of the lowest attenuation pole is 19 GHz or higher. be. By moving the attenuation pole frequency to a higher frequency range than the frequency band used in this way, the attenuation region of the filter module 102 can be widened.

<< Third Embodiment >>
In the third embodiment, a filter module in which the circuit connected between the connection point between the first inductor L1 and the second inductor L2 and the ground is different from the examples shown so far is shown.

FIG. 9A is a circuit diagram of the filter module 103 according to the third embodiment. FIG. 9B is an equivalent circuit diagram of the filter module 103. The filter module 103 includes a circuit board 20 on which a ground electrode is formed, and a bandpass filter 13.

The bandpass filter 13 includes a first terminal T1, a second terminal T2, and a ground terminal GND. Further, the bandpass filter 13 includes a first inductor L1, a second inductor L2 and capacitors C11 and C12, and a first inductor L1 and a second inductor connected in series between the first terminal T1 and the second terminal T2. A parallel circuit of the capacitor C2 and the third inductor L3 connected between the connection portion CP with L2 and the ground terminal GND is provided.

The bandpass filter 13 is connected to the series between the first terminal T1 and the second terminal T2 by the circuit by the first inductor L1, the second inductor L2 and the capacitors C11 and C12, and the first inductor L1. The bandpass filter characteristic is shown by the parallel circuit of the third inductor L3 and the capacitor C2 connected between the connection point between the and the second inductor L2 and the ground.

An inductance component such as a parasitic inductance is generated between the connection portion CP between the first inductor L1 and the second inductor L2 and the ground terminal GND shown in FIG. 9A. In FIG. 9B, this inductance component is represented by an inductor Lp.

As shown in FIG. 9B, when the circuit by the first inductor L1 and the second inductor L2 is represented by the T-type equivalent circuit by the inductors LA, LB, and LC, the inductor LC representing the mutual inductance is the inductor LA connected in series. It is connected between the connection point of the LB and the ground terminal GND. Since the first inductor L1 and the second inductor L2 are connected in harmony, the inductance of the inductor LA is (L1 + M), the inductance of the inductor LB is (L2 + M), and the inductance of the inductor LC is (−M).

The ground electrode of the circuit board 20 is a reference potential electrode of the circuit board 20, and is usually an electrode that spreads over a wide area. As shown in FIG. 9B, an inductance component Lg such as a parasitic inductance is generated between the reference potential electrode of the circuit board 20 and the ground terminal connection pad to which the ground terminal GND of the bandpass filter 13 is connected.

In FIG. 9B, the combined inductance of the inductance component Lg, the inductance component Lp, and the mutual inductance (−M) generated between the ground electrode of the circuit board 20 and the ground terminal GND of the bandpass filter 13 is larger than 0. That is, when the inductance of the inductance component Lg is represented by Lg and the inductance of the inductance component Lp is represented by Lp, (Lp + Lg−M) ≧ 0.

With the above configuration, due to the negative mutual inductance (-M) generated in the path shunted to the ground terminal GND due to the magnetic field coupling between the first inductor L1 and the second inductor L2, the first inductor L1 and the second inductor L2 The inductance component generated between the connection portion CP of the circuit board 20 and the ground electrode of the circuit board 20 is suppressed. Therefore, the inductance of the path connected to the shunt in the region higher than the parallel resonance frequency of the third inductor L3 and the capacitor C2 is suppressed, and the amount of attenuation in the region higher than the passage region becomes larger.

FIG. 10 is a diagram showing the frequency characteristics of the transmission coefficient of the bandpass filter 13. The horizontal axis of FIG. 10 is the frequency, and the vertical axis is the transmission coefficient. In FIG. 10, the characteristic A is the characteristic of the bandpass filter 13 of the present embodiment, and the characteristic B is the characteristic of the bandpass filter as a comparative example. The characteristic B is a characteristic when the mutual inductance M shown in FIG. 9B is set to 0.

Comparing the characteristic A of the bandpass filter 13 of the present embodiment with the characteristic B of the bandpass filter of the comparative example, the center frequency of the pass band is about 2.4 GHz in both cases, but the characteristic B of the low-pass filter of the comparative example. In the low-pass filter 11 of the present embodiment, the decay pole frequency is 12.5 GHz, whereas the decay pole frequency of the above is 8.5 GHz.

The bandpass filter 13 of the present embodiment has a larger amount of attenuation in the higher frequency range than the attenuation pole, as compared with the bandpass filter as a comparative example showing the characteristic B. This is because the inductance component Lp generated between the connection portion CP between the first inductor L1 and the second inductor L2 and the ground terminal GND is suppressed by the negative mutual inductance (−M).

<< Fourth Embodiment >>
In the fourth embodiment, the electronic device including the filter module or the filter element shown above will be exemplified.

FIG. 11 is a block diagram showing the configuration of the electronic device 201 according to the fourth embodiment. The electronic device 201 is, for example, a so-called smartphone or mobile phone device. The electronic device 201 includes a duplexer 53, an antenna 54, a control circuit 50, an interface and a memory 51, and a frequency synthesizer 52. The transmission system includes a transmitter 61, a transmission signal processing circuit 62, a transmission mixer 63, a transmission filter 64, and a power amplifier 65. The reception system includes a low noise amplifier 71, a reception filter 72, a reception mixer 73, a reception signal processing circuit 74, and a handset 75. The transmission signal output from the power amplifier 65 is output to the antenna 54 via the duplexer 53. Further, the signal received by the antenna 54 is amplified by the low noise amplifier 71 via the duplexer 53. In the case of data communication instead of a call, the control circuit 50 processes the received signal.

The filter module or filter element of the present invention can be applied to the transmission filter 64 and the reception filter 72. Further, the filter module or filter element of the present invention can be applied to the filter on the low frequency side of the duplexer 53.

Further, when filters are provided before and after the power amplifier 65, before and after the low noise amplifier 71, before and after the transmission mixer 63, before and after the reception mixer 73, etc., the filter module or filter element of the present invention can be applied to those filters.

In addition, since current smartphones and mobile phone devices are used in multiple antennas and multiple frequency bands, bandpass filters and demultiplexers are often used. As these bandpass filters and demultiplexers, low-pass filters are often used. It can also be configured by combining the filter module or filter element of the present invention having filter characteristics with a high-pass filter.

Finally, the present invention is not limited to the above-described embodiment. It can be appropriately modified and changed by those skilled in the art. The scope of the invention is indicated by the claims, not by the embodiments described above. Further, the scope of the present invention includes modifications and modifications from the embodiments within the scope of the claims and within the scope of the claims.

C1, C2, C3, C11, C12 ... Capacitors C2a, C2b, C2c ... Capacitor electrodes CL1, CL2 ... Coiled conductors CL1a, CL1b, CL1c, CL1d ... Coiled conductors CL2a, CL2b, CL2c, CL2d ... Coiled conductors CP ... Connections E1, E2, E3, E4 ... Side terminal electrodes EGND ... Ground terminal electrode ET1 ... 1st terminal electrode ET2 ... 2nd terminal electrode GND ... Ground terminal L1 ... 1st inductor L2 ... 2nd inductor L3 ... 3rd inductor LA, LB, LC ... Inductor Lg, Lp ... Inductance component M ... Mutual inductance S1 to S11 ... Insulator layer T1 ... First terminal T2 ... Second terminal V ... Interlayer connection conductor WA ... Winding shaft 1 ... Laminated body 10 ... Low-pass filter 11 ... Low-pass filter (filter element)
13 ... Bandpass filter (filter element)
20 ... Circuit board 30 ... Ground electrode 31 ...

Wiring electrodes

32A, 32B ... Interlayer connection conductor 50 ... Control circuit 51 ... Memory 52 ... Frequency synthesizer 53 ... Duplexer 54 ... Antenna 61 ... Transmitter 62 ... Transmission signal processing circuit 63 ... Transmission Mixer 64 ... Transmission filter 65 ... Power amplifier 71 ... Low noise amplifier 72 ... Receive filter 73 ... Receive mixer 74 ... Receive signal processing circuit 75 ...

Handset

101, 102, 103 ... Filter module 201 ... Electronic equipment

Claims

A filter module composed of a circuit board on which a ground electrode is formed and a filter element mounted on the circuit board.
The filter element is
The first inductor and the second inductor, which are connected in series between the first terminal and the second terminal and are magnetically coupled to each other, are connected between the connection portion between the first inductor and the second inductor and the ground terminal. With a capacitor,
The first inductor and the second inductor are connected in sum and are connected.
The mutual inductance generated between the connection portion and the ground terminal due to the magnetic field coupling between the first inductor and the second inductor is represented by M, and the inductance between the connection portion and the ground terminal is Lp and the ground. When the inductance of the path between the terminal and the ground electrode is expressed by Lg, there is a relationship of Lp + Lg-M ≧ 0 and Lp-M <0.
Filter module.
The inductance Lp, the inductance Lg, and the mutual inductance M have a relationship of Lp + Lg−M> 0.
The filter module according to claim 1.
It has a third inductor that is connected in parallel to the capacitor.
The filter module according to claim 1 or 2.
The first inductor and the second inductor are composed of coiled conductors formed in a laminated body of a plurality of insulator layers.
The capacitor is composed of a capacitor electrode facing each other in the stacking direction of the plurality of insulator layers and the insulator layer.
Looking in the winding axis direction of the coiled conductor, the coiled conductor has at least a portion that does not overlap the capacitor electrode.
The filter module according to any one of claims 1 to 3.
The first terminal is composed of a first terminal electrode formed on the laminated body, and the second terminal is composed of a second terminal electrode formed on the laminated body.
Looking in the winding axis direction of the coiled conductor, the capacitor electrode has a portion that does not overlap with at least one of the first terminal electrode and the second terminal electrode.
The filter module according to claim 4.
A filter element mounted on a circuit board on which a ground electrode is formed.
A ground terminal connected to the ground electrode, a first inductor and a second inductor connected in series between the first terminal and the second terminal and magnetically coupled to each other, and the first inductor and the second inductor. A capacitor connected between the connection portion and the ground terminal is provided.
The first inductor and the second inductor are connected in sum and are connected.
When the mutual inductance generated between the connection portion and the ground terminal due to the magnetic field coupling between the first inductor and the second inductor is represented by M, and the inductance between the connection portion and the ground terminal is represented by Lp. , Lp-M <0 relationship,
Filter element.
An electronic device including the filter module according to any one of claims 1 to 5 or the filter element according to claim 6.